What is the problem or limitation you are having?

Some page titles and subheadings in Toga's docs are in title case, and some only have their first word capitalized. For example, the below screenshot shows "API design" next to "Data Sources", and "Supported Platforms" next to "Toga APIs by platform".

Describe the solution you'd like

I think we should pick one approach and stick to it. Personally, I'd vote for title case, since... they're titles.

Describe alternatives you've considered

We could also commit to first-word capitalizing. The sentence/phrase-like tutorial titles (e.g. "You put a box inside another box...") might read more naturally that way.

Edit: Chosen approach

All titles should be first-word-only capitalized, and the tutorial's sentence-like titles should be replaced with "real" titles.

Additional context

No response